Characterization of protein conformational changes is a crucial pre-requisite to understanding biological functions on a molecular level. Circular dichroism (CD) spectroscopy has been an essential component of the biophysical tool kit for decades, exploiting the chiral properties of small molecules, proteins and nucleic acids to provide information on molecular structure and its changes. For example, changes in secondary structure caused by protein unfolding (induced by perturbants such as temperature or pH), or folding (induced by the binding of a small molecule ligand, protein, or nucleic acid) can be quickly and easily quantified as changes in the far-UV CD spectrum. Separately, CD spectroscopy is also an essential technique in the study of chiral-selective properties of small molecules, including drugs, fluorescent dyes, and chemical catalysts designed to mimic enzymatic catalysis. Over the past decade, advancements in instrument optics, as well as the development of additional functionalities such as simultaneous fluorescence detection, and seamless integration with stopped-flow kinetic devices, have further enhanced the utility of CD spectroscopy for biomedical studies. This proposal, in response to Program Announcement PAR-09-028, requests funds to purchase a state-of-the-art CD spectropolarimeter to further the research goals of University of Notre Dame scientists. This instrument will replace our current Cary/Aviv instrument, which although still productive and carefully maintained for its >25 years of life, is now optically and electronically obsolete. The new instrument will be housed in a recently renovated and expanded core facility, and represents one piece of a large effort currently underway to expand and improve research infrastructure at the University Of Notre Dame. As such, supervision, care and maintenance of this instrument create employment opportunities through core facility staff expansion, while access to this state-of-the-art research equipment will continue to grow the research enterprise efforts at Notre Dame.